The noises of vehicle transmissions are no longer completely masked by the engine noise in motor vehicles having hybrid drive or fully-electric drive. Transmission noises which arise due to the rolling of the gearwheel pairs of a transmission can therefore be perceived by the vehicle occupants and found to be annoying. The study of the noise behavior of gear teeth has developed in the course of the trend toward hybrid drives or fully-electric drives in recent years from a marginal discipline of university research to an important quality feature in the industrial production of transmissions.
It has been shown that solely a manufacturing reduction of the deviations of gear teeth from their setpoint geometry, as are determined in conventional isolated defect testing, does not necessarily also result in better noise behavior of the gear teeth in the noise testing and/or rolling testing. Gear teeth susceptible to noise can thus be manufactured more precisely upon observation of the individual defect testing than gear teeth which are not susceptible to noise. The demand therefore exists for the production of gear teeth of maintaining the specified manufacturing tolerances, on the one hand, and additionally meeting the specifications for the noise behavior, on the other hand.
The noises of gear teeth arise due to the tooth contact, i.e., the rolling of the tooth flanks. To analyze dominant frequencies of gear teeth susceptible to noise, a noise measured during the rolling of gear teeth is converted into an order spectrum, for example, with the aid of Fourier transform.
In addition to the orders of tooth engagement, such an order spectrum also has so-called “phantom orders”, which cannot be influenced by the design of the gear teeth and result from manufacturing faults. Dominant phantom orders can arise, for example, due to chucking faults, tool faults, defective bearings, or the axial feed inside a machine tool. It is apparent, for example, that wobbling of a tool during the production of the gear teeth reproduces a periodically repeating deviation from the setpoint geometry on the tooth flanks. This deviation can be geometrically captured using precise coordinate measuring devices.
In many cases, a relationship can be established between the waviness which can be geometrically captured on the surfaces of the tooth flanks and the acoustically detectable, dominant phantom orders. Therefore, a potentially critical noise behavior of gear teeth and/or the state of a machine tool can be concluded with the aid of the geometrical capture of surface waviness of gear teeth.